在Objective-C中比较ios中的多个图像

Question

i am comparing images with each other here is the code for it.

for (int i=0; i<arrImageData.count; i++)
{
    for (int j=i+1; j<arrImageData.count; j++)
    {
        if ([arrImageData[i]isEqualToData:arrImageData[j]])
        {
            [arrImages addObject:arrImage[i]];
        }
    }
}

now problem is when number of images increase it takes too much time to calculate.is there any better solution for it?

Answer 1

you should use hashes to compare big amount of data

1 you can compare UImage directrly: image1.hash == image2.hash

2 you can calculate your own hash for each image added to the array, it will be calculated once and used for every comparison

here is the hash algorithm https://en.wikipedia.org/wiki/MD5

PS it will works if image data is absolutely equal, it much more difficult to compare two different images with one "content" Image comparison - fast algorithm

Answer 2

I think you should use hashes for comparison. Refer this link: Generate hash from UIImage It will help you.

Answer 3

you can try something like this:

- (BOOL)image:(UIImage *)image1 isEqualTo:(UIImage *)image2{    
    return [UIImagePNGRepresentation(image1) isEqual:UIImagePNGRepresentation(image2)];
}

Answer 4

You can use Fast Enumeration as Below

    for(UIImage *img in arrImageData)
    {
        for (UIImage *comImg in arrImageData) {
            if ([UIImageJPEGRepresentation(img, 0) isEqual:UIImageJPEGRepresentation(comImg, 0)]) {
                [arrImages addObject:img];
            }
        }
    }

Hope it helps you...!